attend a long shooting school. Use h4350 powder, good brass like lapua or alpha ,and bullets like berger and Hornady. this would be a good start. my tikka upr likes 140gr berger elite hunter the best.
i have a custom built 338 rum with a terminus action and a 27 inch bartlien barrel. i shoot a 300g berger with 93.8g h1000 at 2900 fps. shoots great. i have not found any begrer bullets or rl33 powder for over a year.